583
FXUS63 KGRR 020715
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
314 AM EDT Sat Aug 2 2025

.KEY MESSAGES...

- Wildfire smoke likely to impact the area this weekend

- Mainly dry and seasonable weather to continue through next week

&&

.DISCUSSION...
Issued at 314 AM EDT Sat Aug 2 2025

- Wildfire smoke likely to impact the area this weekend

Guidance from Michigan EGLE and run to run consistency from smoke
models like with the HRRR indicate that smoke will return to most of
the area through today. Some of it will float down from Northern
Lower where visibilities indicate that it is in place at the sfc
already, and quite a bit will mix down in place this afternoon. The
product AQAGRR has more specifics directly passed on from EGLE.

- Mainly dry and seasonable weather to continue through next week

Aside from the smoke, high confidence remains with regards to a
mainly dry pattern through much of next week, with seasonable
temperatures, and comfortable dew points into early next week before
increasing.

Sfc ridging will be directly overhead through Sunday as we will
remain downstream of a lower amplitude upper ridge. A lack of any
significant flow will keep dew points low in the 40s and 50s. That
dry air combined with the subsidence will keep us dry through Sunday.

The sfc ridge reorients itself, and shifts to Ontario by early next
week. We will still be under the ridge axis, but the subsidence
weakens some as a result. A quite dry atmosphere will continue to
limit rain chances combined with still subsidence in place.

Small rain chances will appear mid-late week, but will be spotty at
best in coverage. This means that a majority of the area will remain
dry through next Friday. The upper ridge weakens a bit as weak short
wave energy tries to flatten it a bit. At the same time, the low
level flow is trying to increase moisture a little bit as it comes
from the Atlantic, vs. from the continental portions of Eastern
Canada. The result will be probably about 20% coverage along lake
breezes that form in the afternoon and coincide with max
heating/diurnal instability.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 125 AM EDT Sat Aug 2 2025

Smoke looks to be the main factor for the forecast for the next 24
hours and beyond. Skies are mainly clear this morning. There is
very little evidence of smoke at this time, although KMKG does
have visibilities down to around 7sm instead of the normal 10sm.
The expectation remains that the smoke will sink south aloft, and
then mix down during the mid afternoon hours. It seems like it
will be enough to drop visibilities to the MVFR range, except
maybe at KMKG where they will have less mixing and somewhat less
smoke with a lake breeze moving inland. It is tough to judge
exactly what visibilities will be in the expected smoke.

Otherwise, we will just have few higher based cumulus clouds mid
afternoon with winds generally remaining from the NE (other than
the lake breeze at KMKG). Winds will go light and variable after
dark. The smoke is expected to hang on overnight.

&&

.MARINE...
Issued at 314 AM EDT Sat Aug 2 2025

After a couple of days of winds and waves increasing late in the
afternoon, we are looking at a few days of relatively light winds
and small waves.

The last couple of days has featured high pressure at the sfc
building in, and working with lower pressures inland to produce
mesoscale wind and wave cores over the lakeshore. Today, and the
next few days will be different with a weak pressure gradient now
established over the area. This will result in winds mainly under 15
knots and waves under 2 ft.

Some smoke will be possible over the lake, reducing visibilities
some. This may be limited as compared to land areas as it appears
much of the smoke will mix down. Less mixing over the relatively
cooler waters leads us to believe this will occur in this scenario.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert until midnight EDT tonight for MIZ037>040-
     043>046-050>052-056>059-064>067-071>074.
MARINE...None.

&&

$$

DISCUSSION...NJJ
AVIATION...NJJ
MARINE...NJJ